Electronic cards such as modem cards, Local Area Network cards (LAN cards) and memory cards are widely used and developed toward minimization. The common standard specifications of electronic cards comprise for example PCMCIA cards, Compact Flash cards (CF cards), Secure Digital memory cards (SD cards), etc. In addition, some new standard specifications are still in development. The contents associated with these specifications are somewhat different. However, the packaging structures of these electronic cards are basically identical. Such packaging structure comprises a metal cover for encapsulating a printed circuit board (PCB). The external surface of the case should be electrically conductive and comprises a ground terminal. After an electronic card is inserted into a slot of an electronic device, the ground terminal will be electrically connected to the system reference of the electronic device for grounding.
The packaging structure of the electronic card needs to provide sufficient mechanical strength and electrical properties, which should meet certain standards requirements. Moreover, it is necessary to produce these electronic cards on a large scale and with low cost. According to the conventional packaging process, top and bottom metal covers with a plurality of bent pieces on the edge thereof are firstly provided. Then, these bent pieces are coupled with a plastic frame. Then, the top and bottom metal covers are riveted by clamp/jig tools. Afterward, the printed circuit board and the plastic frame are encapsulated. As known, the bent pieces fail to be tightly coupled with the plastic frame and the mechanical strengths for the top metal cover and the bottom metal cover are insufficient. Therefore, the metal covers are easily loosened or fallen off when an external force or a deflection force is exerted. Moreover, the packaging structure formed by means of riveting has poor mechanical strength, and thus results in deformation of the metal cover.
Other processes for assembling an electronic card are developed. However, such processes usually use the metal covers with bent pieces on the edges thereof. When an external force or a deflection force is exerted on the electronic card, the bonding regions between the plastic frame and the metal cover are readily separated due to the insufficient force. These processes have been described, for example, in U.S. Pat. Nos. 5,379,587, 5,475,919 and 5,490,891, and Taiwanese Patent Nos. 577624, 111188, 489590 and 549688.